Complicated electronic systems often include multiple equipment cabinets or computers. A multitude of cables typically couple between these computers to provide high-speed data transfers, clocking, and other functions. Unfortunately, these cables also relay electromagnetic interference (EMI) into the surrounding environment. The computers, equipment and cabling must therefore be properly shielded against EMI to prevent unwanted coupling of noise from one computer to another, to prevent radiation of EMI into the environment, and to reduce susceptibility of the equipment to EMI from external sources.
Common solutions to EMI shielding include the shortening of cable length and the utilization of grounded metal coverings (e.g., a coaxial cable). Electrical designers also attempt to eliminate EMI from the source, often by attached capacitors and other components; however, this approach is not often practical unless the designers also manufacture the source of EMI.
As electronic systems increase in speed and complexity, the difficulties associated with EMI shielding similarly increase. There is therefore the need to improve EMI shielding within electronic systems. In particular, there is the need to improve EMI shielding between connected computers and/or equipment cabinets of such systems. The objects of the invention serve to address these needs. Other objects of the invention are apparent within the description that follows.
The invention in one aspect provides an EMI cable shield termination apparatus. The apparatus includes (a) a cable exit panel coupled to a first electronic system and (b) one or more clamps coupled to the exit panel. The exit panel serves as an interface for one or more cables coupled to the first electronic system; the clamps provide mechanical coupling, and EMI shielding, for the cables to that interface. The exit panel couples to electrical ground such as through connection to the chassis of the first electronic system. The clamps also couple to ground through connection with the exit panel. Preferably, one end of the cables attaches to the clamps, at the interface formed by the exit panel, and the other end of the cables attach to respective ferrules coupled to a second electronics system. In preferred aspects of the invention, the first and second electronic systems are computers; and each of the clamps forms at least one aperture (xe2x80x9cclamp aperturexe2x80x9d) to affix to a cable coupled to the first electronic system.
In one aspect, the ferrules attach to chassis ground of the second electronics system. Accordingly, the ferrules function similarly to the clamps attached to chassis ground within the first electronics system. Beneficially, the apparatus of the invention reduces or inhibits EMI effects (e.g., noise) generated from the first electronic system and coupled into the second electronic system.
In the preferred aspect, each of the clamps is formed of two parts; the two parts couple together with one or more screws. The two parts also form at least one clamp aperture when joined together. When in use, the clamp aperture grips a cable in a xe2x80x9cclamshellxe2x80x9d configuration, known in the art, when the clamp screws are tightened in connecting the two parts. Preferably, the clamps are made from nickel plated aluminum, though those skilled in the art should appreciate that other conductive metals, with or without corrosion-resistant coatings, may be used without departing from the scope of the invention.
In one aspect, one or more of the clamps forms first and second apertures for interfacing with first and second cables of a cable pair; the first cable being affixed within the first aperture, the second cable being affixed within the second aperture. Clamps may have additional or fewer apertures as a matter of design choice.
In another aspect, the apparatus has an array of xe2x80x9cNxe2x80x9d clamps supporting (a) up to N cables or (b) up to N cable pairs. If any clamp aperture is not used, the apparatus preferably includes a blank EMI plug, integrated with the aperture, to inhibit EMI noise therethrough. Preferably, any vacant clamp aperture is sealed with a blank EMI plug.
In yet another aspect, the clamps have one or more ribs for enhancing contact and retention to cables and/or blank plugs coupled to clamp apertures.
In still another aspect, one or more of the cables of the apparatus include a hard point contact circumferentially protecting the cable from structural damage at the clamp aperture.
The invention is next described further in connection with preferred embodiments, and it will become apparent that various additions, subtractions, and modifications can be made by those skilled in the art without departing from the scope of the invention.